#include <iostream>
#include <algorithm>

using namespace std;

const int N = 510;
int f[N][N], w[N][N];
int n;

int main() {
    cin >> n;
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= i; ++j)
            cin >> w[i][j];

    for (int i = 1; i <= n; ++i) f[n][i] = w[n][i];

    for (int i = n - 1; i; --i)
        for (int j = 1; j <= i; ++j)
            f[i][j] = max(f[i + 1][j] + w[i][j], f[i + 1][j + 1] + w[i][j]);

    cout << f[1][1] << endl;
    return 0;
}